DIS185SSI4F AIR COMPRESSOR • OPERATION MANUAL — REV. #0 (12/19/16) — PAGE 61
TRAILER GUIDELINES
Next number
: This two-digit number is the wheel or rim
diameter in inches. If you change your wheel size, you
will have to purchase new tires to match the new wheel
diameter.
Next number
: This two- or three-digit number is the tire’s
load index. It is a measurement of how much weight each
tire can support. You may fi nd this information in your
owner’s manual. If not, contact a local tire dealer.
Note
:
You may not fi nd this information on all tires because it is
not required by law.
M+S
: The “M+S” or “M/S” indicates that the tire has
some mud and snow capability. Most radial tires have
these markings; hence, they have some mud and snow
capability.
Speed Rating
: The speed rating denotes the speed at
which a tire is designed to be driven for extended periods
of time. The ratings range from 99 miles per hour (mph) to
186 mph. These ratings are listed in Table A. Note: You may
not fi nd this information on all tires because it is not required
by law.
U.S. DOT Tire Identifi cation Number
: This begins with the
letters “DOT” and indicates that the tire meets all federal
standards. The next two numbers or letters are the plant
code where it was manufactured, and the last four numbers
represent the week and year the tire was built. For example,
the numbers 3197 means the 31st week of 1997. The other
numbers are marketing codes used at the manufacturer’s
discretion. This information is used to contact consumers
if a tire defect requires a recall.
Tire Ply Composition and Materials Used
: The number of
plies indicates the number of layers of rubber-coated fabric
Table A. Speed Rating
Letter Rating
Speed Rating
Q
99 mph
R
106 mph
S
112 mph
T
118 mph
U
124 mph
H
130 mph
V
149 mph
W
168* mph
Y
186* mph
in the tire. In general, the greater the number of plies, the
more weight a tire can support. Tire manufacturers also
must indicate the materials in the tire, which include steel,
nylon, polyester, and others.
Maximum Load Rating
: This number indicates the
maximum load in kilograms and pounds that can be carried
by the tire.
Maximum Permissible Infl ation Pressure
: This number
is the greatest amount of air pressure that should ever be
put in the tire under normal driving conditions.
Uniform Tire Quality Grading Standards (UTQGS)
Treadwear Number
: This number indicates the tire’s
wear rate. The higher the treadwear number is, the longer
it should take for the tread to wear down. For example, a
tire graded 400 should last twice as long as a tire graded
200.
Traction Letter:
This letter indicates a tire’s ability to stop
on wet pavement. A higher graded tire should allow you
to stop your car on wet roads in a shorter distance than a
tire with a lower grade. Traction is graded from highest to
lowest as “AA”,”A”, “B”, and “C”.
Temperature Letter:
This letter indicates a tire’s
resistance to heat. The temperature grade is for a tire that
is infl ated properly and not overloaded. Excessive speed,
underinfl ation or excessive loading, either separately or
in combination, can cause heat build-up and possible tire
failure. From highest to lowest, a tire’s resistance to heat
is graded as “A”, “B”, or “C”.
Refer to Figure J for additional tire information for light
trucks.
Figure J. UTQGS Tire Information
